1 //===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the LoopInfo class that is used to identify natural loops
11 // and determine the loop depth of various nodes of the CFG. Note that natural
12 // loops may actually be several loops that share the same header node.
14 // This analysis calculates the nesting structure of loops in a function. For
15 // each natural loop identified, this analysis identifies natural loops
16 // contained entirely within the loop and the basic blocks the make up the loop.
18 // It can calculate on the fly various bits of information, for example:
20 // * whether there is a preheader for the loop
21 // * the number of back edges to the header
22 // * whether or not a particular block branches out of the loop
23 // * the successor blocks of the loop
28 //===----------------------------------------------------------------------===//
30 #ifndef LLVM_ANALYSIS_LOOP_INFO_H
31 #define LLVM_ANALYSIS_LOOP_INFO_H
33 #include "llvm/Pass.h"
34 #include "llvm/ADT/DepthFirstIterator.h"
35 #include "llvm/ADT/GraphTraits.h"
36 #include "llvm/ADT/SmallVector.h"
37 #include "llvm/Analysis/Dominators.h"
38 #include "llvm/Support/CFG.h"
39 #include "llvm/Support/raw_ostream.h"
45 static void RemoveFromVector(std::vector<T*> &V, T *N) {
46 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
47 assert(I != V.end() && "N is not in this list!");
54 template<class N, class M> class LoopInfoBase;
55 template<class N, class M> class LoopBase;
57 //===----------------------------------------------------------------------===//
58 /// LoopBase class - Instances of this class are used to represent loops that
59 /// are detected in the flow graph
61 template<class BlockT, class LoopT>
64 // SubLoops - Loops contained entirely within this one.
65 std::vector<LoopT *> SubLoops;
67 // Blocks - The list of blocks in this loop. First entry is the header node.
68 std::vector<BlockT*> Blocks;
71 LoopBase(const LoopBase<BlockT, LoopT> &);
73 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &);
75 /// Loop ctor - This creates an empty loop.
76 LoopBase() : ParentLoop(0) {}
78 for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
82 /// getLoopDepth - Return the nesting level of this loop. An outer-most
83 /// loop has depth 1, for consistency with loop depth values used for basic
84 /// blocks, where depth 0 is used for blocks not inside any loops.
85 unsigned getLoopDepth() const {
87 for (const LoopT *CurLoop = ParentLoop; CurLoop;
88 CurLoop = CurLoop->ParentLoop)
92 BlockT *getHeader() const { return Blocks.front(); }
93 LoopT *getParentLoop() const { return ParentLoop; }
95 /// contains - Return true if the specified basic block is in this loop
97 bool contains(const BlockT *BB) const {
98 return std::find(block_begin(), block_end(), BB) != block_end();
101 /// iterator/begin/end - Return the loops contained entirely within this loop.
103 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
104 typedef typename std::vector<LoopT *>::const_iterator iterator;
105 iterator begin() const { return SubLoops.begin(); }
106 iterator end() const { return SubLoops.end(); }
107 bool empty() const { return SubLoops.empty(); }
109 /// getBlocks - Get a list of the basic blocks which make up this loop.
111 const std::vector<BlockT*> &getBlocks() const { return Blocks; }
112 typedef typename std::vector<BlockT*>::const_iterator block_iterator;
113 block_iterator block_begin() const { return Blocks.begin(); }
114 block_iterator block_end() const { return Blocks.end(); }
116 /// isLoopExit - True if terminator in the block can branch to another block
117 /// that is outside of the current loop.
119 bool isLoopExit(const BlockT *BB) const {
120 typedef GraphTraits<BlockT*> BlockTraits;
121 for (typename BlockTraits::ChildIteratorType SI =
122 BlockTraits::child_begin(const_cast<BlockT*>(BB)),
123 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
130 /// getNumBackEdges - Calculate the number of back edges to the loop header
132 unsigned getNumBackEdges() const {
133 unsigned NumBackEdges = 0;
134 BlockT *H = getHeader();
136 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
137 for (typename InvBlockTraits::ChildIteratorType I =
138 InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
139 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
146 //===--------------------------------------------------------------------===//
147 // APIs for simple analysis of the loop.
149 // Note that all of these methods can fail on general loops (ie, there may not
150 // be a preheader, etc). For best success, the loop simplification and
151 // induction variable canonicalization pass should be used to normalize loops
152 // for easy analysis. These methods assume canonical loops.
154 /// getExitingBlocks - Return all blocks inside the loop that have successors
155 /// outside of the loop. These are the blocks _inside of the current loop_
156 /// which branch out. The returned list is always unique.
158 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
159 // Sort the blocks vector so that we can use binary search to do quick
161 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
162 std::sort(LoopBBs.begin(), LoopBBs.end());
164 typedef GraphTraits<BlockT*> BlockTraits;
165 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
166 for (typename BlockTraits::ChildIteratorType I =
167 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
169 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
170 // Not in current loop? It must be an exit block.
171 ExitingBlocks.push_back(*BI);
176 /// getExitingBlock - If getExitingBlocks would return exactly one block,
177 /// return that block. Otherwise return null.
178 BlockT *getExitingBlock() const {
179 SmallVector<BlockT*, 8> ExitingBlocks;
180 getExitingBlocks(ExitingBlocks);
181 if (ExitingBlocks.size() == 1)
182 return ExitingBlocks[0];
186 /// getExitBlocks - Return all of the successor blocks of this loop. These
187 /// are the blocks _outside of the current loop_ which are branched to.
189 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
190 // Sort the blocks vector so that we can use binary search to do quick
192 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
193 std::sort(LoopBBs.begin(), LoopBBs.end());
195 typedef GraphTraits<BlockT*> BlockTraits;
196 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
197 for (typename BlockTraits::ChildIteratorType I =
198 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
200 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
201 // Not in current loop? It must be an exit block.
202 ExitBlocks.push_back(*I);
205 /// getExitBlock - If getExitBlocks would return exactly one block,
206 /// return that block. Otherwise return null.
207 BlockT *getExitBlock() const {
208 SmallVector<BlockT*, 8> ExitBlocks;
209 getExitBlocks(ExitBlocks);
210 if (ExitBlocks.size() == 1)
211 return ExitBlocks[0];
215 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
216 typedef std::pair<const BlockT*,const BlockT*> Edge;
217 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
218 // Sort the blocks vector so that we can use binary search to do quick
220 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
221 std::sort(LoopBBs.begin(), LoopBBs.end());
223 typedef GraphTraits<BlockT*> BlockTraits;
224 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
225 for (typename BlockTraits::ChildIteratorType I =
226 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
228 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
229 // Not in current loop? It must be an exit block.
230 ExitEdges.push_back(std::make_pair(*BI, *I));
233 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
234 /// These are the blocks _outside of the current loop_ which are branched to.
235 /// This assumes that loop is in canonical form.
237 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
238 // Sort the blocks vector so that we can use binary search to do quick
240 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
241 std::sort(LoopBBs.begin(), LoopBBs.end());
243 std::vector<BlockT*> switchExitBlocks;
245 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
247 BlockT *current = *BI;
248 switchExitBlocks.clear();
250 typedef GraphTraits<BlockT*> BlockTraits;
251 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
252 for (typename BlockTraits::ChildIteratorType I =
253 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
255 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
256 // If block is inside the loop then it is not a exit block.
259 typename InvBlockTraits::ChildIteratorType PI =
260 InvBlockTraits::child_begin(*I);
261 BlockT *firstPred = *PI;
263 // If current basic block is this exit block's first predecessor
264 // then only insert exit block in to the output ExitBlocks vector.
265 // This ensures that same exit block is not inserted twice into
266 // ExitBlocks vector.
267 if (current != firstPred)
270 // If a terminator has more then two successors, for example SwitchInst,
271 // then it is possible that there are multiple edges from current block
272 // to one exit block.
273 if (std::distance(BlockTraits::child_begin(current),
274 BlockTraits::child_end(current)) <= 2) {
275 ExitBlocks.push_back(*I);
279 // In case of multiple edges from current block to exit block, collect
280 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
282 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
283 == switchExitBlocks.end()) {
284 switchExitBlocks.push_back(*I);
285 ExitBlocks.push_back(*I);
291 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
292 /// block, return that block. Otherwise return null.
293 BlockT *getUniqueExitBlock() const {
294 SmallVector<BlockT*, 8> UniqueExitBlocks;
295 getUniqueExitBlocks(UniqueExitBlocks);
296 if (UniqueExitBlocks.size() == 1)
297 return UniqueExitBlocks[0];
301 /// getLoopPreheader - If there is a preheader for this loop, return it. A
302 /// loop has a preheader if there is only one edge to the header of the loop
303 /// from outside of the loop. If this is the case, the block branching to the
304 /// header of the loop is the preheader node.
306 /// This method returns null if there is no preheader for the loop.
308 BlockT *getLoopPreheader() const {
309 // Keep track of nodes outside the loop branching to the header...
312 // Loop over the predecessors of the header node...
313 BlockT *Header = getHeader();
314 typedef GraphTraits<BlockT*> BlockTraits;
315 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
316 for (typename InvBlockTraits::ChildIteratorType PI =
317 InvBlockTraits::child_begin(Header),
318 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI)
319 if (!contains(*PI)) { // If the block is not in the loop...
320 if (Out && Out != *PI)
321 return 0; // Multiple predecessors outside the loop
325 // Make sure there is only one exit out of the preheader.
326 assert(Out && "Header of loop has no predecessors from outside loop?");
327 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
329 if (SI != BlockTraits::child_end(Out))
330 return 0; // Multiple exits from the block, must not be a preheader.
332 // If there is exactly one preheader, return it. If there was zero, then
333 // Out is still null.
337 /// getLoopLatch - If there is a single latch block for this loop, return it.
338 /// A latch block is a block that contains a branch back to the header.
339 /// A loop header in normal form has two edges into it: one from a preheader
340 /// and one from a latch block.
341 BlockT *getLoopLatch() const {
342 BlockT *Header = getHeader();
343 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
344 typename InvBlockTraits::ChildIteratorType PI =
345 InvBlockTraits::child_begin(Header);
346 typename InvBlockTraits::ChildIteratorType PE =
347 InvBlockTraits::child_end(Header);
348 if (PI == PE) return 0; // no preds?
354 if (PI == PE) return 0; // only one pred?
357 if (Latch) return 0; // multiple backedges
361 if (PI != PE) return 0; // more than two preds
366 //===--------------------------------------------------------------------===//
367 // APIs for updating loop information after changing the CFG
370 /// addBasicBlockToLoop - This method is used by other analyses to update loop
371 /// information. NewBB is set to be a new member of the current loop.
372 /// Because of this, it is added as a member of all parent loops, and is added
373 /// to the specified LoopInfo object as being in the current basic block. It
374 /// is not valid to replace the loop header with this method.
376 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
378 /// replaceChildLoopWith - This is used when splitting loops up. It replaces
379 /// the OldChild entry in our children list with NewChild, and updates the
380 /// parent pointer of OldChild to be null and the NewChild to be this loop.
381 /// This updates the loop depth of the new child.
382 void replaceChildLoopWith(LoopT *OldChild,
384 assert(OldChild->ParentLoop == this && "This loop is already broken!");
385 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
386 typename std::vector<LoopT *>::iterator I =
387 std::find(SubLoops.begin(), SubLoops.end(), OldChild);
388 assert(I != SubLoops.end() && "OldChild not in loop!");
390 OldChild->ParentLoop = 0;
391 NewChild->ParentLoop = static_cast<LoopT *>(this);
394 /// addChildLoop - Add the specified loop to be a child of this loop. This
395 /// updates the loop depth of the new child.
397 void addChildLoop(LoopT *NewChild) {
398 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
399 NewChild->ParentLoop = static_cast<LoopT *>(this);
400 SubLoops.push_back(NewChild);
403 /// removeChildLoop - This removes the specified child from being a subloop of
404 /// this loop. The loop is not deleted, as it will presumably be inserted
405 /// into another loop.
406 LoopT *removeChildLoop(iterator I) {
407 assert(I != SubLoops.end() && "Cannot remove end iterator!");
409 assert(Child->ParentLoop == this && "Child is not a child of this loop!");
410 SubLoops.erase(SubLoops.begin()+(I-begin()));
411 Child->ParentLoop = 0;
415 /// addBlockEntry - This adds a basic block directly to the basic block list.
416 /// This should only be used by transformations that create new loops. Other
417 /// transformations should use addBasicBlockToLoop.
418 void addBlockEntry(BlockT *BB) {
419 Blocks.push_back(BB);
422 /// moveToHeader - This method is used to move BB (which must be part of this
423 /// loop) to be the loop header of the loop (the block that dominates all
425 void moveToHeader(BlockT *BB) {
426 if (Blocks[0] == BB) return;
427 for (unsigned i = 0; ; ++i) {
428 assert(i != Blocks.size() && "Loop does not contain BB!");
429 if (Blocks[i] == BB) {
430 Blocks[i] = Blocks[0];
437 /// removeBlockFromLoop - This removes the specified basic block from the
438 /// current loop, updating the Blocks as appropriate. This does not update
439 /// the mapping in the LoopInfo class.
440 void removeBlockFromLoop(BlockT *BB) {
441 RemoveFromVector(Blocks, BB);
444 /// verifyLoop - Verify loop structure
445 void verifyLoop() const {
447 assert (getHeader() && "Loop header is missing");
448 assert (getLoopPreheader() && "Loop preheader is missing");
449 assert (getLoopLatch() && "Loop latch is missing");
450 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
455 void print(raw_ostream &OS, unsigned Depth = 0) const {
456 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
459 for (unsigned i = 0; i < getBlocks().size(); ++i) {
461 BlockT *BB = getBlocks()[i];
462 WriteAsOperand(OS, BB, false);
463 if (BB == getHeader()) OS << "<header>";
464 if (BB == getLoopLatch()) OS << "<latch>";
465 if (isLoopExit(BB)) OS << "<exit>";
469 for (iterator I = begin(), E = end(); I != E; ++I)
470 (*I)->print(OS, Depth+2);
478 friend class LoopInfoBase<BlockT, LoopT>;
479 explicit LoopBase(BlockT *BB) : ParentLoop(0) {
480 Blocks.push_back(BB);
484 class Loop : public LoopBase<BasicBlock, Loop> {
488 /// isLoopInvariant - Return true if the specified value is loop invariant
490 bool isLoopInvariant(Value *V) const;
492 /// isLoopInvariant - Return true if the specified instruction is
495 bool isLoopInvariant(Instruction *I) const;
497 /// makeLoopInvariant - If the given value is an instruction inside of the
498 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
499 /// Return true if the value after any hoisting is loop invariant. This
500 /// function can be used as a slightly more aggressive replacement for
503 /// If InsertPt is specified, it is the point to hoist instructions to.
504 /// If null, the terminator of the loop preheader is used.
506 bool makeLoopInvariant(Value *V, bool &Changed,
507 Instruction *InsertPt = 0) const;
509 /// makeLoopInvariant - If the given instruction is inside of the
510 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
511 /// Return true if the instruction after any hoisting is loop invariant. This
512 /// function can be used as a slightly more aggressive replacement for
515 /// If InsertPt is specified, it is the point to hoist instructions to.
516 /// If null, the terminator of the loop preheader is used.
518 bool makeLoopInvariant(Instruction *I, bool &Changed,
519 Instruction *InsertPt = 0) const;
521 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
522 /// induction variable: an integer recurrence that starts at 0 and increments
523 /// by one each time through the loop. If so, return the phi node that
524 /// corresponds to it.
526 /// The IndVarSimplify pass transforms loops to have a canonical induction
529 PHINode *getCanonicalInductionVariable() const;
531 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
532 /// the canonical induction variable value for the "next" iteration of the
533 /// loop. This always succeeds if getCanonicalInductionVariable succeeds.
535 Instruction *getCanonicalInductionVariableIncrement() const;
537 /// getTripCount - Return a loop-invariant LLVM value indicating the number of
538 /// times the loop will be executed. Note that this means that the backedge
539 /// of the loop executes N-1 times. If the trip-count cannot be determined,
540 /// this returns null.
542 /// The IndVarSimplify pass transforms loops to have a form that this
543 /// function easily understands.
545 Value *getTripCount() const;
547 /// getSmallConstantTripCount - Returns the trip count of this loop as a
548 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
549 /// of not constant. Will also return 0 if the trip count is very large
551 unsigned getSmallConstantTripCount() const;
553 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
554 /// trip count of this loop as a normal unsigned value, if possible. This
555 /// means that the actual trip count is always a multiple of the returned
556 /// value (don't forget the trip count could very well be zero as well!).
558 /// Returns 1 if the trip count is unknown or not guaranteed to be the
559 /// multiple of a constant (which is also the case if the trip count is simply
560 /// constant, use getSmallConstantTripCount for that case), Will also return 1
561 /// if the trip count is very large (>= 2^32).
562 unsigned getSmallConstantTripMultiple() const;
564 /// isLCSSAForm - Return true if the Loop is in LCSSA form
565 bool isLCSSAForm() const;
567 /// isLoopSimplifyForm - Return true if the Loop is in the form that
568 /// the LoopSimplify form transforms loops to, which is sometimes called
570 bool isLoopSimplifyForm() const;
573 friend class LoopInfoBase<BasicBlock, Loop>;
574 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
577 //===----------------------------------------------------------------------===//
578 /// LoopInfo - This class builds and contains all of the top level loop
579 /// structures in the specified function.
582 template<class BlockT, class LoopT>
584 // BBMap - Mapping of basic blocks to the inner most loop they occur in
585 std::map<BlockT *, LoopT *> BBMap;
586 std::vector<LoopT *> TopLevelLoops;
587 friend class LoopBase<BlockT, LoopT>;
589 void operator=(const LoopInfoBase &); // do not implement
590 LoopInfoBase(const LoopInfo &); // do not implement
593 ~LoopInfoBase() { releaseMemory(); }
595 void releaseMemory() {
596 for (typename std::vector<LoopT *>::iterator I =
597 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I)
598 delete *I; // Delete all of the loops...
600 BBMap.clear(); // Reset internal state of analysis
601 TopLevelLoops.clear();
604 /// iterator/begin/end - The interface to the top-level loops in the current
607 typedef typename std::vector<LoopT *>::const_iterator iterator;
608 iterator begin() const { return TopLevelLoops.begin(); }
609 iterator end() const { return TopLevelLoops.end(); }
610 bool empty() const { return TopLevelLoops.empty(); }
612 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
613 /// block is in no loop (for example the entry node), null is returned.
615 LoopT *getLoopFor(const BlockT *BB) const {
616 typename std::map<BlockT *, LoopT *>::const_iterator I=
617 BBMap.find(const_cast<BlockT*>(BB));
618 return I != BBMap.end() ? I->second : 0;
621 /// operator[] - same as getLoopFor...
623 const LoopT *operator[](const BlockT *BB) const {
624 return getLoopFor(BB);
627 /// getLoopDepth - Return the loop nesting level of the specified block. A
628 /// depth of 0 means the block is not inside any loop.
630 unsigned getLoopDepth(const BlockT *BB) const {
631 const LoopT *L = getLoopFor(BB);
632 return L ? L->getLoopDepth() : 0;
635 // isLoopHeader - True if the block is a loop header node
636 bool isLoopHeader(BlockT *BB) const {
637 const LoopT *L = getLoopFor(BB);
638 return L && L->getHeader() == BB;
641 /// removeLoop - This removes the specified top-level loop from this loop info
642 /// object. The loop is not deleted, as it will presumably be inserted into
644 LoopT *removeLoop(iterator I) {
645 assert(I != end() && "Cannot remove end iterator!");
647 assert(L->getParentLoop() == 0 && "Not a top-level loop!");
648 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
652 /// changeLoopFor - Change the top-level loop that contains BB to the
653 /// specified loop. This should be used by transformations that restructure
654 /// the loop hierarchy tree.
655 void changeLoopFor(BlockT *BB, LoopT *L) {
656 LoopT *&OldLoop = BBMap[BB];
657 assert(OldLoop && "Block not in a loop yet!");
661 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
662 /// list with the indicated loop.
663 void changeTopLevelLoop(LoopT *OldLoop,
665 typename std::vector<LoopT *>::iterator I =
666 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
667 assert(I != TopLevelLoops.end() && "Old loop not at top level!");
669 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
670 "Loops already embedded into a subloop!");
673 /// addTopLevelLoop - This adds the specified loop to the collection of
675 void addTopLevelLoop(LoopT *New) {
676 assert(New->getParentLoop() == 0 && "Loop already in subloop!");
677 TopLevelLoops.push_back(New);
680 /// removeBlock - This method completely removes BB from all data structures,
681 /// including all of the Loop objects it is nested in and our mapping from
682 /// BasicBlocks to loops.
683 void removeBlock(BlockT *BB) {
684 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
685 if (I != BBMap.end()) {
686 for (LoopT *L = I->second; L; L = L->getParentLoop())
687 L->removeBlockFromLoop(BB);
695 static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
696 const LoopT *ParentLoop) {
697 if (SubLoop == 0) return true;
698 if (SubLoop == ParentLoop) return false;
699 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
702 void Calculate(DominatorTreeBase<BlockT> &DT) {
703 BlockT *RootNode = DT.getRootNode()->getBlock();
705 for (df_iterator<BlockT*> NI = df_begin(RootNode),
706 NE = df_end(RootNode); NI != NE; ++NI)
707 if (LoopT *L = ConsiderForLoop(*NI, DT))
708 TopLevelLoops.push_back(L);
711 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
712 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node?
714 std::vector<BlockT *> TodoStack;
716 // Scan the predecessors of BB, checking to see if BB dominates any of
717 // them. This identifies backedges which target this node...
718 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
719 for (typename InvBlockTraits::ChildIteratorType I =
720 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
722 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
723 TodoStack.push_back(*I);
725 if (TodoStack.empty()) return 0; // No backedges to this block...
727 // Create a new loop to represent this basic block...
728 LoopT *L = new LoopT(BB);
731 BlockT *EntryBlock = BB->getParent()->begin();
733 while (!TodoStack.empty()) { // Process all the nodes in the loop
734 BlockT *X = TodoStack.back();
735 TodoStack.pop_back();
737 if (!L->contains(X) && // As of yet unprocessed??
738 DT.dominates(EntryBlock, X)) { // X is reachable from entry block?
739 // Check to see if this block already belongs to a loop. If this occurs
740 // then we have a case where a loop that is supposed to be a child of
741 // the current loop was processed before the current loop. When this
742 // occurs, this child loop gets added to a part of the current loop,
743 // making it a sibling to the current loop. We have to reparent this
746 const_cast<LoopT *>(getLoopFor(X)))
747 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
748 // Remove the subloop from it's current parent...
749 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
750 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
751 typename std::vector<LoopT *>::iterator I =
752 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
753 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
754 SLP->SubLoops.erase(I); // Remove from parent...
756 // Add the subloop to THIS loop...
757 SubLoop->ParentLoop = L;
758 L->SubLoops.push_back(SubLoop);
761 // Normal case, add the block to our loop...
762 L->Blocks.push_back(X);
764 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
766 // Add all of the predecessors of X to the end of the work stack...
767 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
768 InvBlockTraits::child_end(X));
772 // If there are any loops nested within this loop, create them now!
773 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
774 E = L->Blocks.end(); I != E; ++I)
775 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
776 L->SubLoops.push_back(NewLoop);
777 NewLoop->ParentLoop = L;
780 // Add the basic blocks that comprise this loop to the BBMap so that this
781 // loop can be found for them.
783 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
784 E = L->Blocks.end(); I != E; ++I)
785 BBMap.insert(std::make_pair(*I, L));
787 // Now that we have a list of all of the child loops of this loop, check to
788 // see if any of them should actually be nested inside of each other. We
789 // can accidentally pull loops our of their parents, so we must make sure to
790 // organize the loop nests correctly now.
792 std::map<BlockT *, LoopT *> ContainingLoops;
793 for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
794 LoopT *Child = L->SubLoops[i];
795 assert(Child->getParentLoop() == L && "Not proper child loop?");
797 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
798 // If there is already a loop which contains this loop, move this loop
799 // into the containing loop.
800 MoveSiblingLoopInto(Child, ContainingLoop);
801 --i; // The loop got removed from the SubLoops list.
803 // This is currently considered to be a top-level loop. Check to see
804 // if any of the contained blocks are loop headers for subloops we
805 // have already processed.
806 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
807 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
808 if (BlockLoop == 0) { // Child block not processed yet...
810 } else if (BlockLoop != Child) {
811 LoopT *SubLoop = BlockLoop;
812 // Reparent all of the blocks which used to belong to BlockLoops
813 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
814 ContainingLoops[SubLoop->Blocks[j]] = Child;
816 // There is already a loop which contains this block, that means
817 // that we should reparent the loop which the block is currently
818 // considered to belong to to be a child of this loop.
819 MoveSiblingLoopInto(SubLoop, Child);
820 --i; // We just shrunk the SubLoops list.
830 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
831 /// of the NewParent Loop, instead of being a sibling of it.
832 void MoveSiblingLoopInto(LoopT *NewChild,
834 LoopT *OldParent = NewChild->getParentLoop();
835 assert(OldParent && OldParent == NewParent->getParentLoop() &&
836 NewChild != NewParent && "Not sibling loops!");
838 // Remove NewChild from being a child of OldParent
839 typename std::vector<LoopT *>::iterator I =
840 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
842 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
843 OldParent->SubLoops.erase(I); // Remove from parent's subloops list
844 NewChild->ParentLoop = 0;
846 InsertLoopInto(NewChild, NewParent);
849 /// InsertLoopInto - This inserts loop L into the specified parent loop. If
850 /// the parent loop contains a loop which should contain L, the loop gets
851 /// inserted into L instead.
852 void InsertLoopInto(LoopT *L, LoopT *Parent) {
853 BlockT *LHeader = L->getHeader();
854 assert(Parent->contains(LHeader) &&
855 "This loop should not be inserted here!");
857 // Check to see if it belongs in a child loop...
858 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
860 if (Parent->SubLoops[i]->contains(LHeader)) {
861 InsertLoopInto(L, Parent->SubLoops[i]);
865 // If not, insert it here!
866 Parent->SubLoops.push_back(L);
867 L->ParentLoop = Parent;
872 void print(raw_ostream &OS) const {
873 for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
874 TopLevelLoops[i]->print(OS);
876 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
877 E = BBMap.end(); I != E; ++I)
878 OS << "BB '" << I->first->getName() << "' level = "
879 << I->second->getLoopDepth() << "\n";
884 class LoopInfo : public FunctionPass {
885 LoopInfoBase<BasicBlock, Loop> LI;
886 friend class LoopBase<BasicBlock, Loop>;
888 void operator=(const LoopInfo &); // do not implement
889 LoopInfo(const LoopInfo &); // do not implement
891 static char ID; // Pass identification, replacement for typeid
893 LoopInfo() : FunctionPass(&ID) {}
895 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
897 /// iterator/begin/end - The interface to the top-level loops in the current
900 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
901 inline iterator begin() const { return LI.begin(); }
902 inline iterator end() const { return LI.end(); }
903 bool empty() const { return LI.empty(); }
905 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
906 /// block is in no loop (for example the entry node), null is returned.
908 inline Loop *getLoopFor(const BasicBlock *BB) const {
909 return LI.getLoopFor(BB);
912 /// operator[] - same as getLoopFor...
914 inline const Loop *operator[](const BasicBlock *BB) const {
915 return LI.getLoopFor(BB);
918 /// getLoopDepth - Return the loop nesting level of the specified block. A
919 /// depth of 0 means the block is not inside any loop.
921 inline unsigned getLoopDepth(const BasicBlock *BB) const {
922 return LI.getLoopDepth(BB);
925 // isLoopHeader - True if the block is a loop header node
926 inline bool isLoopHeader(BasicBlock *BB) const {
927 return LI.isLoopHeader(BB);
930 /// runOnFunction - Calculate the natural loop information.
932 virtual bool runOnFunction(Function &F);
934 virtual void releaseMemory() { LI.releaseMemory(); }
936 virtual void print(raw_ostream &O, const Module* M = 0) const;
938 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
940 /// removeLoop - This removes the specified top-level loop from this loop info
941 /// object. The loop is not deleted, as it will presumably be inserted into
943 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
945 /// changeLoopFor - Change the top-level loop that contains BB to the
946 /// specified loop. This should be used by transformations that restructure
947 /// the loop hierarchy tree.
948 inline void changeLoopFor(BasicBlock *BB, Loop *L) {
949 LI.changeLoopFor(BB, L);
952 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
953 /// list with the indicated loop.
954 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
955 LI.changeTopLevelLoop(OldLoop, NewLoop);
958 /// addTopLevelLoop - This adds the specified loop to the collection of
960 inline void addTopLevelLoop(Loop *New) {
961 LI.addTopLevelLoop(New);
964 /// removeBlock - This method completely removes BB from all data structures,
965 /// including all of the Loop objects it is nested in and our mapping from
966 /// BasicBlocks to loops.
967 void removeBlock(BasicBlock *BB) {
971 static bool isNotAlreadyContainedIn(const Loop *SubLoop,
972 const Loop *ParentLoop) {
974 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop,
980 // Allow clients to walk the list of nested loops...
981 template <> struct GraphTraits<const Loop*> {
982 typedef const Loop NodeType;
983 typedef LoopInfo::iterator ChildIteratorType;
985 static NodeType *getEntryNode(const Loop *L) { return L; }
986 static inline ChildIteratorType child_begin(NodeType *N) {
989 static inline ChildIteratorType child_end(NodeType *N) {
994 template <> struct GraphTraits<Loop*> {
995 typedef Loop NodeType;
996 typedef LoopInfo::iterator ChildIteratorType;
998 static NodeType *getEntryNode(Loop *L) { return L; }
999 static inline ChildIteratorType child_begin(NodeType *N) {
1002 static inline ChildIteratorType child_end(NodeType *N) {
1007 template<class BlockT, class LoopT>
1009 LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
1010 LoopInfoBase<BlockT, LoopT> &LIB) {
1011 assert((Blocks.empty() || LIB[getHeader()] == this) &&
1012 "Incorrect LI specified for this loop!");
1013 assert(NewBB && "Cannot add a null basic block to the loop!");
1014 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
1016 LoopT *L = static_cast<LoopT *>(this);
1018 // Add the loop mapping to the LoopInfo object...
1019 LIB.BBMap[NewBB] = L;
1021 // Add the basic block to this loop and all parent loops...
1023 L->Blocks.push_back(NewBB);
1024 L = L->getParentLoop();
1028 } // End llvm namespace